Fig. 4. Intact An. stephensi tubules. (A) Control tubules subjected to alkaline phosphatase staining protocol without chromogenic substrate; the junction with the gut is shown with an arrow; (B) as in A but subjected to alkaline phosphatase staining protocol in the presence of NBT/BCIP chromogenic substrate; the junction with the gut is shown with an arrow; (C) DAPI-stained; (D) as in C but also stained for alkaline phosphatase; (E) high-magnification view of lightly stained lower tubule, revealing predominantly apical staining. Scale bars, 100 µm for A-D; 10 µm for E.